Conventionally, WC powder is synthesized by solid phase reaction by mixing together tungsten powder and solid-phase carbon powder, and carburizing the mixture at high temperature. However, since the synthesis method by solid phase reaction involves reducing the initial powder to fine particles by means of a mechanical milling process, it is rather difficult to produce WC powder with particle size of 0.5 μm or less.
Meanwhile, in the 1990's and thereafter, there was commercialization of a synthesis technique, so-called liquid-phase reaction. This is a synthesis technique of obtaining ultra-fine WC/Co powder by using aqueous metal salt by spray-drying such aqueous solution containing W and Co. However, because of the growth of WC particles during the processes of drying aqueous solution, reduction, and carburization heat treatment, this type of synthesis process using liquid-phase posed limitation in producing ultra-fine powder of 0.1 μm or less.